1. Field of the Invention
The present invention relates generally to a probe card and more particularly to an electrical contact device of a probe card with good reliability.
2. Description of the Related Art
In the process of fabrication of semiconductor chips, the chips have to be tested for the circuited function prior to package process. The testing procedure provides an electrical contact between the machine and the chips via an electrical contact device, such as probe card. The electrical contact device has probes in contact with the pads of the chip. The machine provides signals to the chip via the probe card, and the signals feedback to the machine to qualify the chip.
A prior art of electrical contact device 80, as shown in FIG. 28, includes a base 81 and probes 82 on the base 81. Each of the probes has a first end 83 bonded to the base 81 and a second end 84 extended over a cavity 85 on the base 81. The second ends 84 of the probes 82 are adapted to contact pads of a chip. Because the second ends 84 of the probes 82 are suspended, it provides the probes 82 with elasticity. With the elasticity, the probes 82 can keep in contact with the pads of the chip.
Another prior art of electrical contact device is shown in FIG. 29, which includes a base 91 and probes 92 also. The probes 92, directly formed on the base 91, have first ends 93 connected to the base 92 and second ends 94 extended over a cavity 95 on the base 91. The probes 92 have elasticity also to contact pads of a chip at the second ends 94 thereof.
However, the size of the semiconductor chips are becoming smaller and the amount of the pads is drastically increasing, so that the density of the probes of the electrical contact device should be higher than before so as to meet the increasing amount and the shrinking size of pads. In terms of the denser population of probes, each suspended probe has to shrink the portions connected to the base consequently. Therefore, during the long-term testing procedure and repeating contact, the connective portions of the probes are inclined to crack and to rip off from the base so as to cause malfunction of the electrical contact device and lower the reliability of probe card.